Scheme Optimization For Jet Grouting Pile Reinforcement Of Soft Ground In Deep Foundation Pit

With the unprecedented development of urban rail transit in our country, there are more and more deep foundation pit engineering examples, the problems is also more and more. As a kind of feasible measure of deformation control, stabilization of soft soil in passive area can effectively change the mechanics index, reduce the consolidation deformation caused by dewatering, enhance the ability to resist uplift bottom, improve the coefficient of passive earth pressure. According to the excavation engineering instance of Dalian Haizhiyun subway station, this paper study the problem of jet grouting pile reinforcement of soft ground in deep foundation pit using the finite element software ABAQUS, optimize the layout of jet grouting pile reinforcement by the results of numerical simulation. The main work is as follows:1. Simulating the foundation pit instance with ABAQUS numerical model, and comparing the results of numerical calculation and field monitoring. The comparison results show that the horizontal displacement of sheet pile and the internal bracing axial forces of numerical simulation and field monitoring is almost the same, which verifies the rationality of the calculation model and paves the way for further study.2. The numerical simulation results show that:the horizontal displacement of sheet pile and the internal bracing axial forces are larger as the excavation deeper; excavating to the pit bottom, the maximum horizontal displacement occur in the soft layer, and the axial force of the fourth support reach the maximum; because of the constraint of the internal bracing, the displacement of the top of supporting pile is outward.3. In the process of soft foundation reinforcement of the passive zone, the efficiency of strip reinforcement and skirt reinforcement decline, as its area increase. So, reasonable strip reinforcement and skirt reinforcement should be within the scope of certain proportion. The way of 1:3 strip reinforcement and 3 rows of skirt reinforcement is used by the project instance, which is an efficient layout scheme of the jet grouting pile.4. The numerical model of reinforced concrete sheet pile is set up separately, loading monitoring displacement, to calculate the stress distribution of concrete and rebar, which meet the design requirements. Simulating the influence of deferent dewatering sequence on foundation pit deformation, it is found that the process of excavation as dewatering is better for the safety of the supporting structure than excavation after dewatering.